Materials Department, University of California, Santa Barbara, CA 93106, USA.
Phys Chem Chem Phys. 2012 Feb 28;14(8):2840-8. doi: 10.1039/c2cp23253g. Epub 2012 Jan 25.
First-principles density functional theory studies have been carried out for native defects and transition-metal (Ti and Ni) impurities in lithium alanate (LiAlH(4)), a potential material for hydrogen storage. On the basis of our detailed analysis of the structure, energetics, and migration of lithium-, aluminium-, and hydrogen-related defects, we propose a specific atomistic mechanism for the decomposition and dehydrogenation of LiAlH(4) that involves mass transport mediated by native point defects. We also discuss how Ti and Ni impurities alter the Fermi-level position with respect to that in the undoped material, thus changing the concentration of charged defects that are responsible for mass transport. This mechanism provides an explanation for the experimentally observed lowering of the temperature for the onset of decomposition and of the activation energy for hydrogen desorption from LiAlH(4).
采用第一性原理密度泛函理论研究了锂铝氢化物（LiAlH(4)）中本征缺陷和过渡金属（Ti 和 Ni）杂质，LiAlH(4)是一种有前途的储氢材料。基于对锂、铝和氢相关缺陷的结构、能量和迁移的详细分析，我们提出了 LiAlH(4)分解和脱氢的特定原子机制，该机制涉及本征点缺陷介导的质量输运。我们还讨论了 Ti 和 Ni 杂质如何改变费米能级相对于未掺杂材料的位置，从而改变负责质量输运的带电缺陷的浓度。该机制解释了实验观察到的 LiAlH(4)分解起始温度和氢解吸活化能降低的原因。
